In a railroad road bed, conventional rails each having a base with a web extending upward therefrom to a head or crown are typically joined together, by fishplates which lap the ends of adjacent rails and are bolted to the webs thereof. To facilitate alignment of the bolt holes in the fish plate and in the web, the holes in the web of the rail may be drilled in the rail when it is in place in the road bed. If a particular rail segment is worn or damaged, then a replacement rail must match the one it replaces. To ensure correct alignment of each rail segment, it is often desirable first to set adjacent segments in place, and only tnen drill holes on site, through the web of each segment to accommodate fastening bolts as aforesaid.
The above described activity is often carried out in remote locations, at times under emergency conditions and sometimes in confined areas, e.g., a tunnel. Regardless of the difficulty of drilling through hard, tough steel under such circumstances, it is essential that the holes be precisely located and quickly and cleanly drilled. The apparatus of choice for this purpose is a rail drill, optionally powerable by a choice of power sources, which can be quickly and precisely aligned and operated by a single trained operator, and which is light enough to be comfortably carried by the operator from rail to rail on site. Suitable power sources for this purpose include electric motors (a.c. if a generator is available, or d.c. if a battery is used) or hydraulic or pneumatic motors (if a high pressure fluid, such as water or air, respectively, is available).
Examples of patents issued on railroad drills include U.S. Pat. No. 3,273,424 to Hughes disclosing a railroad drill whose height above the crown of the rail to which it is clamped, to drill one or more holes in the web thereof, is adjustable by two screws. The vertical locations of holes are referenced to the top of the rail crown, hence wear of the crown must be correctly determined and allowed for in using the drill. Also, accidental or careless change in their adjustment could result in serious error in vertically positioning the holes. The Hughes drill is long enough to span the gap between conventionally spaced parallel rails and uses both rails to support its weight in use and, therefore, would be unsuitable for use on a single rail or dangerous when it is necessary to drill between a rail and a live third rail.
U.S. Pat. No. 3,706,505 to Stougaard, discloses a portable railroad drill which clamps onto the crown of the rail to be drilled and is partially supported by a pair of adjustable ground-engaging legs. The Stougaard drill can be adjusted vertically with respect to the clamped rail crown and can be positioned along the rail at preselected locations once the clamp is tightened onto the rail. Careful vertical adjustment, taking rail wear into account, would be required to avoid vertical hole-position errors.
U.S. Pat. No. 3,945,749 to McIlrath discloses a clamping apparatus for a railroad drill which employs a ground-engaging support remote from the clamp. The McIlrath clamping mechanism comprises a pair of long cylindrical drill-unit supporting guide rods above both the rail and the drill axis. The movable jaw of the McIlrath clamp is guided to move normal to the rail by an aperture therein sliding over a cantilevered rod protruding from the clamp head. The McIlrath clamp employs a pair of clamping blocks to fit the rail profile on the drill side. Both the McIlrath and Stougaard drills appear to be both bulky and heavy, requiring an operating crew at least two workmen to move them about and to align them correctly with respect to the workpiece particularly in adjusting the ground support.
A need exists, therefore, for a light portable railroad drill mechanism that can be carried and operated in relatively confined quarters by a single trained operator, which clamps onto a rail or other workpiece at a vertical web without needing alignment with respect to a wearing surface of the workpiece. It should, preferably, allow the use of the most advanced drill bits for operation by a variety of power sources.
It is accordingly an object of the present invention to provide a drill having a light, sturdy, and highly portable power drill clamping mechanism that can be easily carried and operated by a single operator.
Another object of this invention is to provide a power drill mechanism that is easily and firmly clamped precisely at predetermined locations marked on a workpiece to be drilled.
Yet another object of this invention is to provide a railroad drill mechanism that can repeatedly drill holes precisely at a predetermined height with respect to the non-wearing profile of the rail being drilled.
A further object of this invention is to provide a railroad drill mechanism that provides for controlled manual feeding of the drill bit in confined spaces.
Yet a further object of this invention is to provide a railroad drill mechanism with an efficient self-oiling annular drill bit.
An even further object of this invention is to provide a clamping apparatus that can be used to clamp a drill to a railroad tie, beam or the like at any orientation of the drill irrespective of the ground surface.